Generally, an image processor, such as a printer, scanner, fax machine, copier, and complex machine combining the functions of those apparatuses, has a communication unit (NIC (Network Interface Card), modem (modulator-demodulator), etc.) that communicates with an external device (computer, another image processor, etc.) via such a communication medium as network and telephone circuit. Some image processors have a plurality of communication units. In many cases, such an image processor works as so-called complex machine that has a function of executing a plurality of types of jobs involving communication processes with external devices through the communication units.
The image processor has, for example, a print function of receiving a print job from an external terminal (personal computer, etc.) through an NIC and printing out based on the print job.
The image processor has other functions, such as a scan data transmission function of transmitting image data read from a manuscript by a scanner of the image processor to another terminal through an NIC.
The image processor having a plurality of communication units is capable of executing a plurality of processes involving communication through the communication units in parallel processing.
For example, an image processor having two NICs (called a first NIC and a second NIC) is assumed. Such an image processor can execute a process involving the print function, using the first NIC, and, in parallel processing, execute a process involving the scan data transmission function (hereinafter “scan job”), using the second NIC.
Conventionally, in an image processing system including an image processor having a plurality of NICs, and terminals capable of communicating with the image processor through the NICs, the communication address (IP address, etc.) of an NIC that is a job transmission destination is preset (stored) at each terminal, so that each terminal is fixed in communication to a specific NIC. In other words, the corresponding relation between the communication units of the image processor and the terminals is fixed in the image processing system.
Japanese Laid-Open Patent Publication No. 2004-221723 discloses a technique that an image processor having a plurality of NICs sends a message to a host computer through a communication unit (NIC) that is determined to be available in sending the message to the host computer.
Regarding an image processing system including an image processor having a plurality of communication units, and terminals capable of communicating with the image processor through the communication units, however, when the corresponding relation between the communication units of the image processor and the terminals is fixed, the system poses a problem of lower job processing efficiency as described below.
When a plurality of terminals send process requests for a plurality of different types of jobs at overlapping timing to the same communication unit of the image processor, the image processor manages to execute only one of the requested jobs even if the jobs can be processed concurrently in parallel processing (e.g., print job and scan job), because the communication unit has to work on overlapping jobs. As a result, the jobs supposed to be processed concurrently in parallel processing cannot be processed concurrently, which leads to lower job processing efficiency.
On the other hand, when a plurality of terminals send process requests for the same kind of jobs at overlapping timing to different communication units of the image processor, no communication unit has to work on overlapping jobs, but the equipment other than communication units that processes the jobs (equipment composing a printing unit carrying out image formation, equipment composing a scanner unit carrying out scanning of manuscript image, etc.) has to work on overlapping jobs. The image processor, therefore, manages to execute only one of the requested jobs. In this case, a job standing by for execution may occupy a communication unit to make impossible the reception of another job that can be processed using the communication unit. As a result, the jobs supposed to be processed concurrently in parallel processing cannot be processed concurrently, which leads to lower job processing efficiency.